Method and device for obtaining candidate information

ABSTRACT

A method, computer readable medium and mobile device for operating using more than one Radio Access Technology (RAT) are provided. When the mobile device is operating in a serving cell of a first RAT, it obtains, through at least one of wireless access radios in the mobile device, a first set of candidate information from a message transmitted for the serving cell. It also obtains, through at least one of the wireless access radios, a second set of candidate information from a message transmitted for a neighbor cell of the serving cell. The mobile device considers the candidate information from the first set and the candidate information from the second set for reselection by the mobile device.

TECHNICAL FIELD

The present application relates to a mobile device configured to operateusing more than one Radio Access Technology (RAT) offered by a carrierand a method for obtaining candidate information while the mobile deviceis operating in a serving cell of a first RAT.

BACKGROUND

Some mobile devices are configured to operate using more than one RadioAccess Technology (RAT). These are known as multi-mode devices. Carriersor service providers that provide services in both 2G (such as GSM[Global System for Mobile Communication] EDGE [Enhanced Data Rates forGSM Evolution]) and 3G (such as UMTS [Universal MobileTelecommunications System]) and possibly other advanced networks such asEPS (Evolved UTRAN (Universal Terrestrial Radio Access Network) and theEvolved Packet Core) may prefer for subscribers to access 3G networks orother advanced networks whenever feasible.

While a multi-mode mobile device in idle mode is in a 2G cell, a networkmay provide information on cells or frequencies with other radio accesstechnologies (excluding E-UTRA) in the 3G Cell Reselection list (see3GPP TS 44.018 Section 3.4.1.2.1.7). For a multi-mode mobile device thatsupports E-UTRA, E-UTRAN frequencies may be included in the E-UTRAN CellReselection list (see 3GPP TS 44.018 Section 3.4.1.2.1.7a). The 3G CellReselection list and the E-UTRAN Cell Reselection list are provided in aSystem Information Type 2quater (S12Q) message.

If the network provides information on UTRAN cells and possibly E-UTRANfrequencies associated with zero or more not allowed physical layer cellidentities (which may be referred to as blacklisted cells) for cellreselection, measurement and reporting, this information is sent in theSI2Q message (see 3GPP TS 44.018 section 3.2.2.1). SI2Q messages aretransmitted on a periodic basis and a mobile device with UTRAN orE-UTRAN capability (i.e. a multi-mode device) is configured to listen tothe SI2Q messages to obtain a list of 3G cells and possibly E-UTRANfrequencies associated with zero or more not allowed physical layer cellidentities which it should measure (or not use in the case of notallowed cell identities). The mobile device measures the neighbour 3Gcells or the E-UTRAN frequencies provided and if at least one of thosemeasured cells or frequencies passes threshold measurements as describedin 3GPP TS 45.008 section 6.4, the mobile device reselects the 3G orE-UTRAN cell that rates the highest based on the measurements. Ifpriority information is to be used for cell reselection (see 3GPP TS44.018 section 3.4.1.2.1.12), which is signalled by the presence of the3G Measurement Control Parameters Description IE or by the presence ofthe E-UTRAN Measurement Parameters Description IE in the S12quatermessage, then the Serving Cell Priority Parameters Description IE isalso present in the SI2quater message in order to provide the servingcell priority and reselection parameters. If the MS receives anyabsolution priorities in dedicated messages (for instance when a call ordata session is released) then these dedicated priorities override thepriorities received in the SI2quater broadcast message.

If the network sends a list of cells associated with frequencies thatare not allowed for reselection (e.g. a blacklist) then this informationis also taken into consideration in the cell reselection procedure.

The list of neighbour cells or frequencies provided in the SI2Q messageis not always accurate. Sometimes the backend data used to determine theneighbours is incorrect. As well, environmental conditions can causeerrors in determining viable 3G cells or E-UTRAN cells. In suchsituations, timely reselection of the 3G network or the E-UTRAN networkis inhibited. This is very visible to the user, as many multi-modemobile devices will display on a user interface an indication of whichRAT is being used.

In addition the list of neighbour cells or neighbour frequenciesprovided by the 3G network or E-UTRAN network, such as the neighbourcells provided in System Information Block Type 11, 11bis or 12 (see3GPP TS 25.331 section 10.2.48.8.14, 10.2.48.8.14a, 10.2.48.8.15) may beinaccurate.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments will now be described in greater detail withreference to the accompanying drawings, in which:

FIGS. 1A, 1B and 1C are diagrams of a system having at least two RATs;

FIG. 2 is a flowchart of a method for obtaining a set of candidateinformation;

FIG. 3 is a flowchart of a further embodiment of the method depicted inFIG. 2;

FIG. 4 is a flowchart of a method for obtaining a set of 3G cells;

FIG. 5 is a diagram of a mobile device on which the methods describedherein may be executed;

FIG. 6 is a diagram of a mobile device on which the methods describedherein may be executed; and

FIG. 7 is a block diagram of a mobile device on which the methodsdescribed herein may be executed.

DETAILED DESCRIPTION

The ability of a mobile device that is configured to operate in 2G, 3G,and possibly other advanced networks such as EPS to quickly reselectback to a 3G or other advanced network after a valid 2G reselection hasoccurred may be inconsistent in some systems today because of theexistence of transient environmental conditions or inconsistent orincomplete network information regarding 3G neighbour cells or E-UTRANneighbour frequencies. In some situations, the System Information 2Quater (SI2Q) for a 2G serving cell does not provide all of the viable3G cells or E-UTRAN frequencies that may be available to the mobiledevice in the serving cell. In more general terms, a mobile deviceconfigured to operate using more than one RAT is provided withinformation from a neighbour cell repository to be used for reselectionto a cell of second RAT while in a serving cell of a first RAT.Sometimes, the information provided is inaccurate and all viable cellsor frequencies on which to search for cells of the second RAT are notprovided to the wireless device.

Similarly a mobile device configured to operate in 2G, 3G and possiblyother advanced networks such as EPS, remains in the current RAT ratherthan a reselecting to another RAT where poor or inconsistent networkinformation about neighbour cells or transient environmental conditionsexist. In some situations, the System Information Block Type 11, 11bisor 12 of the serving cell in the 3G network does not provide all theviable 3G cells or E-UTRAN frequencies that may be available to themobile device in the serving cell. In more general terms, a mobiledevice configured to operate using more than one RAT is provided withinformation about neighbours cells in another RAT. Sometimes, theinformation provided in the current RAT is inaccurate and all the viablecells or frequencies on which to search for cells are not provided tothe wireless device.

According to one aspect of the present invention, there is provided amobile device configured to operate using more than one Radio AccessTechnology (RAT), the mobile device comprising: for each radio accesstechnology, a respective wireless access radio; a cell selectorconfigured to, while the mobile device is operating in a serving cell ofa first RAT: obtain, through at least one of the wireless access radios,a first set of candidate information from a message transmitted for theserving cell; obtain, through at least one of the wireless accessradios, a second set of candidate information from a message transmittedfor a neighbour cell of the serving cell; and consider the candidateinformation from the first set and the candidate information from thesecond set in determining a cell for reselection by the mobile device.

According to another aspect of the present invention, there is provideda method for obtaining candidate information while a mobile device isoperating in a serving cell of a first RAT, the method comprising:obtaining a first set of candidate information from a message for theserving cell; obtaining a second set of candidate information from amessage transmitted for a neighbour cell; and considering the candidateinformation from the first set and the candidate information from thesecond set in determining a cell for reselection by the mobile device.

According to still another aspect of the present invention, there isprovided a tangible computer readable medium having computer readableinstructions stored thereon that when executed control a mobile deviceto implement a method for obtaining candidate information of a secondRadio Access Technology (RAT) while the mobile device is operating in aserving cell of a first RAT, the method comprising: obtaining a firstset of candidate information of the second RAT from a messagetransmitted for the serving cell; obtaining a second set of candidateinformation of the second RAT from a message transmitted for a neighbourcell of the serving cell; and considering the candidate information fromthe first set and the candidate information from the second set indetermining a cell for reselection by the mobile device.

Thus, in another aspect there is provided a mobile device configured tooperate using more than one Radio Access Technology (RAT), the mobiledevice comprising: for each radio access technology, a respectivewireless access radio; a cell selection/reselection module configuredto, when the mobile device is operating in a serving cell of a firstRAT: obtain, through at least one of the wireless access radios, atleast one of a first set of candidate cells, or frequencies that may beassociated with a first set of not allowed cells of a second RAT from amessage transmitted for the serving cell; obtain, through at least oneof the wireless access radios, at least one of a second set of candidatecells, or frequencies that may be associated with a second set of notallowed cells of the second RAT from a message transmitted for aneighbour cell of the serving cell; and consider at least one of thecandidate cells or frequencies and associated not allowed cells from thefirst set and the candidate cells or frequencies and associated notallowed cells from the second set for reselection by the mobile device.

In another aspect, there is provided a method for obtaining at least oneof candidate cells or frequencies and not allowed cells of the secondRadio Access Technology (RAT) while a mobile device is operating in aserving cell of a first RAT, the method comprising: obtaining at leastone of a first set of candidate cells or frequencies and associated notallowed cells of the second RAT from a message for the serving cell;obtaining at least one of a second set of candidate cells or frequenciesand associated not allowed cells or frequencies of the second RAT from amessage transmitted for a neighbour cell of a serving cell; andconsidering at least one of the candidate cells or frequencies and notallowed cells from the first set and the candidate cells or frequenciesand not allowed cells from the second set for reselection by the mobiledevice.

In another aspect, there is provided a tangible computer readable mediumhaving computer readable instructions stored thereon that when executedcontrol a mobile device to implement a method for obtaining candidatecells or frequencies of a second Radio Access Technology (RAT) while themobile device is operating in a serving cell of a first RAT, the methodcomprising: obtaining at least one of a first set of candidate cells orfrequencies and associated not allowed cells of the second RAT from amessage transmitted for the serving cell; obtaining at least one of asecond set of candidate cells or frequencies and associated not allowedcells of the second RAT from a message transmitted for a neighbour cellof the serving cell; and considering at least one of the candidate cellsor frequencies and not allowed cells from the first set and thecandidate cells or frequencies and not allowed cells from the second setfor reselection by the mobile device.

In another aspect, there is provided a method for obtaining at least oneof candidate cells or frequencies and associated not allowed cells of asecond Radio Access Technology (RAT) while a mobile device is operatingin a serving cell of the second RAT, the method comprising: obtaining atleast one of a first set of candidate cells or frequencies andassociated not allowed cells of the second RAT from a messagetransmitted for a neighbour cell in a first RAT; and considering atleast one of the candidate cells or frequencies and not allowed cellsfrom the first set and the candidate cells or frequencies and notallowed cells from the second set for reselection by the mobile device.

Referring now to FIG. 1A, a system 100 is shown comprising networks 180and 190 of two RATs. In other embodiments of the system, there may benetworks of any number of RATs. A first network 180 provides service formobile devices operating using a first RAT and a second network 190provides coverage for mobile devices operating using a second RAT. Inthe system 100, the coverage areas of the two networks 180 and 190 areoverlapping. Each network 180 and 190 is comprised of a number of cellsor frequencies (not shown in FIG. 1A). In some networks cells aregrouped by frequency. For example, in E-UTRAN a center frequencycomprises a plurality of cells. A neighbour cell repository 110transmits messages for cells or frequencies of the first network 180 orthe second network 190 or both. In 2G networks, for example, each cellhas a designated frequency and the messages for each cell aretransmitted on the respective frequency for the cell. In E-UTRAN, eachcenter frequency is shared by more than one cell. Non-limiting examplesof information in the messages can comprise available cells, availablefrequencies, not allowed cells, and priorities of cells or frequencies.Non-limiting examples of the messages transmitted include SI3, SI13 andSI2Q, which are described in detail in 3GPP TS 44.018 section 9.1.

Referring now to FIG. 1B, an embodiment of the first network 180 orsecond network 190 comprises areas. For illustrative purposes only, twoareas 120 and 130 are shown. In 2G, these areas may comprise Local Areas(LA) and Routing Areas (RA). In E-UTRAN, the network comprises trackingareas. In an embodiment of the system 100, there is a serving cell 130of a first RAT, as well as two neighbour cells 132 and 134 of the firstRAT within an area of overlapping LA and RA. The serving cell 130 is acell where service is presently being provided to a mobile device. FIG.1B shows two overlapping areas 120 and 130 for illustrative purposesonly. In other embodiments, there can be any number of areas and theymay or may not be overlapping.

Referring to FIG. 1C, in an embodiment, there are four cells orfrequencies of a second RAT 142, 144, 146 and 148 that overlap theserving cell 130. The particular arrangements shown in FIG. 1A, 1B or 1Care for illustrative purposes only. There can be any number of neighbourcells or frequencies and any number of cells or frequencies of thesecond RAT. Each cell does not necessarily abut or overlap another cell.Furthermore, there can be gaps and overlaps between any of the cells ofthe first RAT and any of the cells of the second RAT. In E-UTRAN cellsare grouped by center frequency and may overlap or have gaps as well.

A network may have policies and priorities for the system 100 such thatmobile devices select a cell of the specific RAT if it is available. Insystems where the RATs are 2G and 3G, an example of such a policy is forthe mobile device to select a 3G cell if one is available. Otherexamples of policies and priorities will be known to those of normalskill in the art.

In an embodiment, the neighbour cell repository 110 provides mobiledevices in the serving cell 130 with a set of neighbour cells orfrequencies of the first RAT. In addition the servicing cell may beprovided a set of cells or frequencies on which to look for cells of thesecond RAT from which the mobile devices may select a cell forreselection. In the example shown in FIG. 1, the set of cells orfrequencies of the second RAT should include all four cells orfrequencies of the second RAT 142, 144, 146 and 148. However, in somesituations the set of cells or frequencies of the second RAT providedfor the serving cell 130 may be incomplete and may be missing one ormore viable cells or frequencies of the second RAT 142, 144, 146 and148. If a mobile device in the serving cell 130 attempts to measure eachof the cells or frequencies provided in the set of cells or frequenciesof the second RAT for the serving cell 130 and none of them are viablefor reselection, the mobile device can obtain a further set of cells orfrequencies of the second RAT, the further set being provided by therepository 110 for at least one of the neighbour cell(s) 132, 134. Ifthe further set of cells or frequencies of the second RAT provided forthe neighbour cell(s) 132, 134 includes cells or frequencies of thesecond RAT that were not the set of cells or frequencies of the secondRAT for the serving cell 130, the mobile device can measure thoseadditional cells or frequencies of the second RAT. In some embodiments,the mobile device can select a cell from those cells or frequenciesmeasured. In some embodiments, the mobile device selects one of thecells or frequencies measured that has at least one parameter thatexceeds a threshold value. In some embodiments, the information providedfor the serving cell and the neighbour cell includes a prioritized listof cells or frequencies. In some embodiments, the information providedfor the serving cell and the neighbour cell includes a list of notallowed cells or frequencies. In addition, the mobile device can storeinformation related to the cells or frequencies of the second RAT on aninternal memory, separately or together with information related to theset of cells or frequencies of the second RAT provided for the servingcell 130.

Referring now to FIG. 2, a method for obtaining candidate informationwhile a mobile device is operating in a serving cell of a first RAT willbe described. Non-limiting examples of candidate information arecandidate cells and candidate frequencies. In some embodiments thecandidate information is candidate cells or frequencies in a second RAT.In some embodiments the first RAT is 2G and the second RAT is 3G. Inother embodiments, the RATs can be any one of 2G, 3G, E-UTRA, 4G or anyother RAT. Non-limiting examples of 2G technologies are GSM (GlobalSystem for Mobile Communications), EDGE (Enhanced Data Rates for GSM)and CDMA IS-95 (Code Division Multiple Access IS-95). Non-limitingexamples of 3G technologies are UMTS (Universal Mobile TelecommunicationSystem) and CDMA 2000.

The method starts at step 220 which is obtaining a first set ofcandidate information from a message transmitted for the serving cell.Next, the method proceeds with obtaining a second set of candidateinformation from a message transmitted for a neighbour cell or neighbourfrequency of the serving cell (Step 222). In some embodiments, forexample if the first RAT is 2G, the message transmitted for the servingcell is transmitted at a frequency different from a frequency of themessage transmitted for the neighbour cell. The final step isconsidering the candidate information from the first set and thecandidate information from the second set in determining a cell forreselection by the mobile device (Step 224). The step of consideringcandidate cells or frequencies in determining a cell for reselection caninclude but is not limited to measuring the candidate cells or cells onthe candidate frequencies and selecting a cell that ranks the highestbased on measured values. Another example of considering candidate cellsfor reselection is attempting to reselect cells or frequencies from thefirst set and if unsuccessful, then attempting to reselect at least onecell or frequency from the second set.

In one embodiment, in a 2G/3G system or 2G/3G/E-UTRAN system or2G/E-UTRAN system, the set of 3G cells or E-UTRAN frequencies providedfor reselection by mobile devices in idle mode currently camped in 2Gcells is obtained from an SI2Q message. Thus, in such a system, toimplement the method of FIG. 2, the mobile device in the serving cellextracts a set of 3G cells and/or E-UTRAN frequencies for at least one2G neighbour cell from at least one SI2Q message transmitted at afrequency designated for the at least one 2G neighbour cell.

In some embodiments the method includes determining at least oneneighbour cell of the serving cell. In some embodiments the at least oneneighbour cell is of the first RAT. In some embodiments where the firstRAT is 2G, the neighbour cell is a 2G neighbour cell in the same LA/RAas the serving cell.

In a further embodiment, the candidate information comprises a set ofnot allowed cells or frequencies.

Referring now to FIG. 3, some embodiments of the method further comprisemeasuring at least one cell or frequency from the second set ofcandidate information. This is shown as step 310 in the flowchart ofFIG. 3, which starts at point A on the flowchart of FIG. 2, immediatelyafter step 224. Measuring can comprise obtaining information related toquality of service in the respective cell or frequency. In 3G, measuringcomprises measuring the Ec/No (Energy per chip over Noise) and RSCP(Received Signal Code Power) of the cell. Details of measuring are foundin 3GPP TS 45.008 section 6.6.4.

In some embodiments, the method further comprises storing informationrelated to any cells or frequencies in the second set of informationthat have at least one parameter that exceeds a threshold value on amemory in the mobile device. This is step 320 of FIG. 3. Non-limitingexamples of information that can be stored for a cell in the set are: anidentifier for the cell; a frequency for the cell; and values ofmeasured parameters. In some mobile devices, the information related tocandidate cells or frequencies in the second set is stored together withinformation related to candidate cells or frequencies from the firstset. In some embodiments, the information stored is consolidated so thatany duplicate information is not stored again. I.e. only informationrelated to candidate cells or frequencies from the second set that isnot already stored on the mobile device will be stored.

The method in some embodiments further comprises selecting a cell orfrequency from the second set that has at least one parameter thatexceeds a threshold value. This is step 330 of FIG. 3. This isadvantageous if, for example, the selected cell or frequency did notappear in the first set of candidate cells or frequencies. The totalnumber of cells or frequencies of the second RAT of which each mobiledevice is aware can thus be larger than the number provided for mobiledevices in the serving cell.

In still further embodiments, the method further comprises ranking thecandidate cells or frequencies of the second set. The ranking can bebased on the values received from measurements, and may also includepriority information received from a network with respect to thecandidate cells or frequencies. The cells or frequencies in the secondset can be ranked together with cells or frequencies of the first set.In this manner, in the E-UTRAN case, for example, the mobile device canselect a cell or frequency on which to search for a cell based on theranking. In some embodiments, the method comprises selecting a cell orfrequency from the ranked cells or frequencies that is ranked highest.In some embodiments, information related to cells or frequencies thatare ranked above a predefined value is stored in a memory on the mobiledevice. In this manner, the mobile device can keep information relatedto the top ranked cells or frequencies of the second RAT. For example, amobile device can be configured to store information related to the top3 or the top 10 cells or frequencies. Depending on the amount of memoryavailable, the information for any number of cells can be stored.

As mentioned above, in some embodiments the method is implemented in asystem having 2G and 3G networks, where there is a policy for subscribermobile devices to select a 3G cell whenever possible. A method forobtaining a set of 3G cells will now be described with reference to FIG.4. At step 410 a mobile device within a 2G serving cell determines atleast one 2G neighbour cell that is in the same LA/RA as the servingcell. Then at step 420, the mobile device obtains a set of 3G cellsprovided for at least one of the 2G neighbour cells in the same LA/RA.At step 430, the mobile device measures at least one of the 3G cells inthe set obtained. Embodiments of this method can also comprise rankingthe 3G cells in the set obtained, either separately or consolidating theranking with a further set of 3G cells provided for the serving 2G cell.In some embodiments this is done in a similar manner as described abovewith reference to FIGS. 2 and 3. Furthermore, information related to the3G cells provided for the neighbour 2G cells can be stored on a memoryon the mobile device. In some embodiments, this information isconsolidated with information already stored on the mobile devicerelated to 3G cells provided for mobile devices in the serving cell.

During normal operation in 2G, a mobile device will decode the SystemInformation 3 (SI3), the System Information 13(SI13) and SystemInformation 2 Quater (SI2Q) from the 2G neighbour cells that are beinglisted as neighbours for the 2G serving cell that the mobile device iscurrently camped on. SI3 contains a Location Area Identification (LAI)for the 2G cell, in accordance with 3GPP TS 44.018 section 9.1.43a, andSI13 contains a Routing Area Code (RAC) for the 2G cell, in accordancewith 3GPP TS 44.018 section 9.1.35. In some embodiments the decoding isperformed by a protocol stack (PS). The mobile device can assess fromthe neighbour 2G cell system information, which 2G cells are of the sameLocation Area (LA) and Routing Area (RA) as the presently serving 2Gcell. The 2G cell information is obtained from SI2/SI2TER for idle mode,in accordance with 3GPP 44.018 sections 9.1.32 and 9.1.34, and fromSI5/SI5TER for dedicated mode, in accordance with 3GPP 44.018 sections9.1.37 and 9.1.39. No network interaction is required to reselect 2Gcells of the same LA and RA. As the network has no way of knowing if themobile device has autonomously reselected to one of these cells, themobile device is free to extract the 3G neighbour cells listed for these2G neighbours from the SI2Q for each neighbour cell, and make additionalIRAT (Inter-Radio Access Technology) 3G measurements against them ascandidates for reselection to 3G. This will increase the number of 3Gcandidates available to the mobile device and will address scenarioswhere a bad network configuration leaves viable 3G candidates off thelist for the serving 2G cell, when they can be easily seen from thephysical location and are seen to be listed in other 2G cells' neighbourlists. Any 3G cell from the lists of the 2G cells in the same LA and RAcan be reselected by the mobile device without the mobile device firstreselecting to one of the neighbour 2G cells.

During normal operation in 3G, a mobile device may decode SystemInformation Block 1 (SIB 1), System Information Block 3(SIB 3) and/orSystem Information Block 4 (SIB 4), System Information Block 11 (SIB 11)and/or System Information Block 11bis (SIB 11bis) and/or SystemInformation Block 11bis (SIB 12) from the 3G neighbour cells, that arebeing listed as neighbours for the 3G serving cell that the mobiledevice is currently camped on. SIB 1 contains a Location AreaIdentification (LAI) for the 3G cell, in accordance with 3GPP TS 25.331section 10.2.48.8.4, and also contains a Routing Area Code (RAC). Themobile device can assess from the neighbour 3G cell system information,which 3G cells are of the same Location Area (LA) and Routing Area (RA)as the presently serving 3G cell. The 3G cell information is obtainedfrom SIB11 or SIB11bis for idle mode, in accordance with 3GPP 25.331sections 8.1.1.6.11 and 8.1.1.6.11a, and from SIB11, SIB11bis or SIB12for connected mode, in accordance with 3GPP 25.331 sections 8.1.1.6.11,8.1.1.6.11a, 8.1.1.6.12. No network interaction is required to reselect3G cells of the same LA and RA. As the network has no way of knowing ifthe mobile device has autonomously reselected to one of these cells, themobile device is free to extract the neighbour cells listed for theseneighbours from the SIB11, SIB11bis and SIB12 for each neighbour cell,and make additional measurements against them as candidates forreselection. This will increase the number of 3G candidates available tothe mobile device and will address scenarios where a bad networkconfiguration leaves viable 3G candidates off the list for the servingcell, when they can be easily seen from the physical location and areseen to be listed in other 3G cells' neighbour lists. Any 3G cell fromthe lists of the 3G cells in the same LA and RA can be reselected by themobile device without the mobile device first reselecting to one of theneighbour 2G cells.

In addition after reselection from 2G to a 3G cell, the candidate cellsfrom SI2Q of the 2G serving cell and additional 3G candidate cells fromSI2Q of the neighbour 2G cells may be stored and utilised in 3G toincrease the number of 3G candidates available but not listed asneighbours in System Information Block 11 (SIB 11) and/or SystemInformation Block 11bis (SIB 11bis) and/or System Information Block11bis (SIB 12). A protocol stack (PS) of a subscriber mobile device maydecode the System Information Block 1 (SIB 1) of these additionalcandidates to determine the LA and RA of these additional cells. Nonetwork interaction is required to reselect 3G cells of the same LA andRA as the network has no way of knowing if the mobile device hasautonomously reselected to one of these cells. This will increase thenumber of 3G candidates available to the mobile device and will addressscenarios where a bad network configuration leaves viable 3G candidatesoff the list for the serving cell, when they can be easily seen from thephysical location and instead of a reselection to another RAT.

In an exemplary embodiment, the following implementation may be used:

1) A mobile device will obtain and keep information on 3G cells fromSI2Q of a predetermined number (for example 2 or 3) of strongest 2Gneighbour cells from the same LA/RA as a camped cell, in addition toSI2Q of the serving cell;

2) If the 3G cells listed in SI2Q_serving (i.e. the SI2Q provided forthe serving cell) as measured in a predetermined number (for exampletwo, three, four, or five) of consecutive measurement attempts do notfulfill reselection criteria, the device will perform detected cellmeasurements on the frequencies listed in SI2Q_serving, whereby themobile device will list all 3G cells that it can resolve on the listedfrequencies;

3) If detected cell measurements do not discover viable 3G cells or ifthe detected cell measurements find cells that are not listed in theSI2Q_serving or the SI2Q_neighbours (i.e. the SI2Q for the two strongestneighbours), the mobile device will ignore the results and fall back tothe regular 3G measurements procedure (step 1) until step 2 is triggeredonce again;

4) If detected cell measurements find a 3G cell that is suitable forreselection and this cell is listed in SI2Q_neighbours, the mobiledevice will consider it for 2G to 3G reselection and start apredetermined (for example 4 or 5 seconds) guard time. The regular cellreselection rules for the service provider will apply; and

5) If the serving 2G cell or 2G neighbour cells are changed, the 3Gcells that are monitored will be changed accordingly.

Of course, the above method only describes one possible implementation.The 3G cells can be obtained from the SI2Q of any number of 2G neighbourcells and any number of measurement attempts can be made. Likewise, theguard time can be any length that is appropriate to ensure that themobile device does not jump to a cell that was only availablemomentarily or for a short period of time. In some embodiments, no guardtime is used.

The methods described herein are implemented on a mobile device. Themethods, in some embodiments, may be implemented using hardware,firmware, computer-readable media having computer-readable instructionsstored thereon or combinations thereof.

One embodiment of a mobile device will now be described with referenceto FIG. 5. A mobile device 500 is configured to operate using more thanone RAT. The mobile device 500 comprises a cell selector 510 and awireless access radio 520 and 530 for each RAT. For illustrativepurposes, the device 500 shown in FIG. 5 has two wireless access radios520 and 530. However, embodiments of mobile devices described herein canhave any number of wireless access radios.

The cell selector 510 is configured to, when the mobile device 500 isoperating in a serving cell of a first RAT, obtain, through at least oneof the wireless access radios 520 and 530, a first set of candidateinformation from a message transmitted for the serving cell. The cellselector 510 also obtains, through at least one of the wireless accessradios 520 and 530, a second set of candidate information from a messagetransmitted for a neighbour cell of the serving cell. The cell selector510 is also configured to consider the candidate information from thefirst set and the candidate information from the second set indetermining a cell for reselection by the mobile device 500.

The mobile device 500, in some embodiments, also comprises a tangiblecomputer readable medium having computer readable instructions storedthereon for implementing the cell selector 510. In other embodiments themobile device 500 further comprises a protocol stack. The cell selectormay be located on the protocol stack. The protocol stack can also beused to decode SI13 and SI2Q messages.

In some embodiments the mobile device 500 also includes a memory forstoring the first set of candidate information and the second set ofcandidate information.

A mobile device 600 comprising a computer readable medium 610, aprotocol stack 620, a memory 630 and two wireless access radios 640 and650 is shown in FIG. 6. The computer readable medium 610 storescomputer-readable instructions for implementing any of the methodsdescribed herein. The protocol stack 620 can store the computer readablemedium 610 or perform decoding functions for the mobile device or both.The memory 630 can store information or data obtained in performing themethods implemented by the computer-readable instructions. The wirelessaccess radios 640 and 650 perform a similar function as wireless accessradios 520 and 530 described with reference to FIG. 5.

Referring now to FIG. 7, shown is a block diagram of a mobile device 700that may implement any of the methods described herein. It is to beunderstood that the mobile device 700 is shown with very specificdetails for example purposes only.

A processing device (a microprocessor 728) is shown schematically ascoupled between a keyboard 714 and a display 726. The microprocessor 728controls operation of the display 726, as well as overall operation ofthe mobile device 700, in response to actuation of keys on the keyboard714 by a user.

The mobile device 700 has a housing that may be elongated vertically, ormay take on other sizes and shapes (including clamshell housingstructures). The keyboard 714 may include a mode selection key, or otherhardware or software for switching between text entry and telephonyentry.

In addition to the microprocessor 728, other parts of the mobile device700 are shown schematically. These include: a communications subsystem770; a short-range communications subsystem 702; the keyboard 714 andthe display 726, along with other input/output devices including a setof LEDS 704, a set of auxiliary I/O devices 706, a serial port 708, aspeaker 711 and a microphone 712; as well as memory devices including aflash memory 716 and a Random Access Memory (RAM) 718; and various otherdevice subsystems 720. The mobile device 700 may have a battery 721 topower the active elements of the mobile device 700. The mobile device700 is in some embodiments a two-way radio frequency (RF) communicationdevice having voice and data communication capabilities. In addition,the mobile device 700 in some embodiments has the capability tocommunicate with other computer systems via the Internet.

Operating system software executed by the microprocessor 728 is in someembodiments stored in a persistent store, such as the flash memory 716,but may be stored in other types of memory devices, such as a read onlymemory (ROM) or similar storage element. In addition, system software,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store, such as the RAM 718. Communication signalsreceived by the mobile device 700 may also be stored to the RAM 718.

The microprocessor 728, in addition to its operating system functions,enables execution of software applications on the mobile device 700. Apredetermined set of software applications that control basic deviceoperations, such as a voice communications module 730A and a datacommunications module 730B, may be installed on the mobile device 700during manufacture. In addition, a personal information manager (PIM)application module 730C may also be installed on the mobile device 700during manufacture. The PIM application is in some embodiments capableof organizing and managing data items, such as e-mail, calendar events,voice mails, appointments, and task items. The PIM application is alsoin some embodiments capable of sending and receiving data items via awireless network 710. In some embodiments, the data items managed by thePIM application are seamlessly integrated, synchronized and updated viathe wireless network 710 with the device user's corresponding data itemsstored or associated with a host computer system.

In addition, a software application to perform a cell selector function730D may be installed. The cell selector function 730D may implement anyof the methods described herein for obtaining a set listing cells orfrequencies of a second Radio Access Technology (RAT) while the mobiledevice is operating in a serving cell of a first RAT.

As well, additional software modules, illustrated as another softwaremodule 730N, may be installed during manufacture.

What has been described is merely illustrative of the application of theprinciples of methods, modules and devices described herein. Otherarrangements and methods can be implemented by those skilled in the artwithout departing from the spirit and scope of the embodiments.

1. A mobile device configured to obtain candidate information for one ormore cells of a second Radio Access Technology (RAT) while operating ina serving cell of a first RAT, the mobile device comprising: for eachRAT, a respective wireless access radio; a cell selector configured to,while the mobile device is operating in the serving cell of the firstRAT: obtain, through at least one of the wireless access radios, a firstset of candidate information from a message transmitted for the servingcell, the first set of candidate information comprising informationconcerning cells or frequencies of the second RAT that are provided ascandidates for cell reselection from the serving cell; obtain, throughat least one of the wireless access radios, a second set of candidateinformation from a message transmitted for a neighbour cell of theserving cell, the second set of candidate information comprisinginformation concerning cells or frequencies of the second RAT that areprovided as candidates for cell reselection from the neighbour cell ofthe serving cell; and consider the candidate information from the firstset and the candidate information from the second set in determining acell for reselection by the mobile device.
 2. The mobile device of claim1, wherein the candidate information comprises candidate cells orcandidate frequencies of the first RAT and the second RAT.
 3. The mobiledevice of claim 1, wherein the cell selector is further configured toobtain, through at least one of the wireless access radios, informationindicating not allowed cells associated with frequencies from at leastone message transmitted for at least one of the first RAT and a secondRAT.
 4. The mobile device of claim 1, wherein the first RAT is 2G or 3G.5. The mobile device of claim 1, wherein the candidate information isfor the second RAT and the second RAT is 3G or E-UTRA.
 6. The mobiledevice of claim 1, further comprising a tangible computer readablemedium having computer readable instructions stored thereon forimplementing the cell selector.
 7. The mobile device of claim 1, furthercomprising a memory for storing the first set of candidate informationand the second set of candidate information.
 8. A method for a mobiledevice to obtain candidate information for one or more cells of a secondRadio Access Technology (RAT) while the mobile device is operating in aserving cell of a first RAT, the method comprising: obtaining a firstset of candidate information from a message for the serving cell, thefirst set of candidate information comprising information concerningcells or frequencies of the second RAT that are provided as candidatesfor cell reselection from the serving cell; obtaining a second set ofcandidate information from a message transmitted for a neighbour cell ofthe serving cell, the second set of candidate information comprisinginformation concerning cells or frequencies of the second RAT that areprovided as candidates for cell reselection from the neighbour cell ofthe serving cell; and considering the candidate information from thefirst set and the candidate information from the second set indetermining a cell for reselection by the mobile device.
 9. The methodof claim 8, wherein candidate information comprises candidate cells orcandidate frequencies from the first RAT and the second RAT.
 10. Themethod of claim 8, wherein the first RAT is 2G and the candidateinformation is for the second RAT, the second RAT being 3G.
 11. Themethod of claim 8, wherein the second set of candidate informationcomprises candidate cells, the method further comprising measuring atleast one cell from the second set.
 12. The method of claim 8, whereinthe second set of candidate information comprises candidate frequencies,the method further comprising measuring at least one frequency from thesecond set in order to search for suitable cells on the at least onefrequency.
 13. The method of claim 8, further comprising storing asubset listing any candidate cells or frequencies from the second setthat have a parameter that exceeds a threshold value on a memory in themobile device.
 14. The method of claim 13, further comprising selectinga candidate cell or frequency from the subset.
 15. The method of claim8, further comprising ranking the candidate cells or frequencies in thesecond set.
 16. The method of claim 15, wherein the candidate cells orfrequencies in the second set are ranked together with the candidatecells or frequencies of first set.
 17. The method of claim 15, furtherwherein ranking of the candidate cells or frequencies takes intoconsideration priority information.
 18. The method of claim 8, whereinthe serving cell is a 2G cell, the neighbour cell or frequency comprisesa predetermined number of strongest 2G neighbour cells, and thecandidate information is for 3G, the method further comprising: making apredetermined number of attempts to measure 3G cells listed in the firstset and if a viable 3G cell is not located, performing detected cellmeasurements on frequencies in which 3G neighbour cells are known fromthe first set to be present; if the detected cell measurements find aviable 3G cell that is listed in the second set, considering the viable3G cell detected for reselection.
 19. The method of claim 8, wherein theneighbour cell is in the same location area and routing area as theserving cell.
 20. A tangible computer readable medium having computerreadable instructions stored thereon that when executed control a mobiledevice to implement a method for obtaining candidate information for oneor more cells of a second Radio Access Technology (RAT) while the mobiledevice is operating in a serving cell of a first RAT, the methodcomprising: obtaining a first set of candidate information of the secondRAT from a message transmitted for the serving cell, the first set ofcandidate information comprising information concerning cells orfrequencies of the second RAT that are provided as candidates for cellreselection from the serving cell; obtaining a second set of candidateinformation of the second RAT from a message transmitted for a neighbourcell of the serving cell, the second set of candidate informationcomprising information concerning cells or frequencies of the second RATthat are provided as candidates for cell reselection from the neighbourcell of the serving cell; and considering the candidate information fromthe first set and the candidate information from the second set indetermining a cell for reselection by the mobile device.